Toucan Smart Field Development: How to Generate More Value from Hydrocarbon Resources

Abstract

Abstract The Toucan Field is an oil rim situated in Gabon, discovered late 2001, operated by Shell Gabon. The joint venture partner is Amerada Hess Production Gabon. Experience from an adjacent field indicates that it is critical to manage the oil rim in such a way that reservoir energy is preserved whilst maximizing oil production. Due to the limited amount of information in this early stage of field development, there is high uncertainty in terms of reservoir properties. The smart technologies applied are directed towards reducing these uncertainties and mitigate down side risks of structural uncertainties. Firstly a smart well completion is described which permits control of drawdown in long horizontal wells where total drawdown must be restricted owing to the proximity of water and gas. The completion instrumentation allows the flow control valve to be positioned using pressure rather than positional information. Based on simulation work, various strategies for well operation are discussed, along with their various merits; both in the context of the well, and the field. Secondly the combination of frequent well tests, production optimization, and the use of reservoir surveillance tools is used to deliver an optimal solution to help the asset team analyze deviations from the expected reservoir performance. The business benefits of these smart technologies are discussed in the context of implementation in a medium sized oil rim. Introduction This paper covers a study done by Shell Gabon and Shell International E&P to investigate the applicability of smart technology to the development of the Toucan oil rim. Compared with a base case development scenario, several technologies have been evaluated: Smart Wells, Smart Well Head Control, Smart Facilities, the Smart Fields Strategy and a method to handle wax deposition. In this paper, a well is considered ‘smart’ when it is equipped with sensors and Flow Control Valves (FCVs) to measure and control the flow from the reservoir to well segments separated from each other by packers. Toucan The Toucan field was discovered by Shell Gabon and its joint venture partner Amerada Hess Production Gabon late 2001. The reservoir comprises a series of sand units unconformably overlain by a further thinner sand layer, and a sealing salt. See Figure 1. The sands are separated by fieldwide shales. The oil accumulation is a thin oil rim (23 m), overlain by a gas cap and underlain by a medium strong to strong aquifer. The sands are highly permeable (multi-Darcy) and the oil is light (32°API), but very waxy. To date, five horizontal wells have been drilled varying in length from 400 to 1200 meters. The wells are completed with a 4.5"slotted liner and 3.5" tubing. One well crosses a thick shale layer. Owing to limited seismic quality (significant overburden effects) and production history, much structural uncertainty still remains. Limited pressure and oil contact data indicate that the intra reservoir shales are at least partly compartmentalising the reservoir. Smart Wells Horizontal wells are well suited for the development of thin oil rims. In Toucan, however, two critical challenges with conventional horizontal wells are expected. Both are related to the low drawdown resulting from Toucan's high permeability, the high off take rates, and the limited drawdown which can applied if coning is to be avoided. Firstly, it has been shown1 that coning occurs in long horizontal wells where the drawdown is in the same order of magnitude as the frictional pressure drop in the wellbore. See Figure 2. A non-uniform drawdown profile therefore results in a sub-optimal development: the wells will produce below its potential and it causes an uneven sweep of the oil rim. In addition, long horizontal wells without Flow Control Valves are more difficult to clean-up after drilling. This concern is supported by PLT results, which show that all appraisal wells produce primarily from the heel.